Recommended Posts

I am trying to connect a 4 to 20mA two wire current transmitter to SM43JR20. I hooked up everything and the PLC is showing some value too. But I am not sure how to properly read the input from the current transmitter in the ladder logic. I tried using linearization with analog input as x data and current value to be displayed as Y data but the value displayed is varying when ever I change the values in the linearization block. I looked at the manual but it is not helping.

I have one more issue, How will you use a constant with decimal point in visilogic eg: 4.5. All I see are integer operands

Share this post

Link to post

Share on other sites

In normal mode, your analog inputs for this PLC have 14-bit resolution. That means the MI attached to the analog input should vary between 0 & 16383. For a 4-20mA input, that value will be 3277-16383. You will then use a linearization block to convert that number to the units you wish to work with. If you want precision that includes one or more decimal places, you will need to use "implied" decimals. For instance, say your input is pressure in psi that ranges from 0 to 100 psi, but you want precision to one decimal place. You need to linearize from 0-1000, instead of 0-100. Now you have the pressure to one decimal place with the decimal point implied. In calculations you may need to divide by 10 at the conclusion of the calculations, or if you're going to display the result, no need to divide by 10 as you can set the location of the decimal point in the numeric display element that you place on the HMI screen.

Share this post

Link to post

Share on other sites

I do not know if you can help me, I need an off delight or commonly called TOF or delay to the disconnection in a PLC unitronics and I do not find that option anywhere I can do? I am new the this comunidsd just looking for a little help

Share this post

Link to post

Share on other sites

This is what your linearization block should look like for the example I described above:

This will linearize the 4-20mA input to 0.0 to 100.0.

But SM43JR20 is a 10 bit PLC, right ? But I understood the theory and I used it on my PLC but still when the sensor is removed the input is read as 0 but the ouput is shown as 3098 which I really don't understand. Can you help with this?

Share this post

Link to post

Share on other sites

You are correct. Not sure which spec document I was looking at, but it was clearly the wrong one. X1 & X2 should be 204 & 1023, respectively. If the value of MI 0 is zero, then you should expect to see something close to -167 for MI 1.

Share this post

Link to post

Share on other sites

Hi all can anybody help me - I struggle to understand to do linearization from my IO-PT400 via EX-RC1 to vision130. The opper hand work on my EX-RC1 and read the temp but struggle to let my Vision 130 read and see it. I actually struggle to understand exactly how to send the data over. Attached is my coding.

Share this post

Link to post

Share on other sites

I see it on the EX-RC1 operands and see how the temp change from the probe but to send it over programming is a problem. I do not see the reading on the vision 130 plc. It is a program issue not a comms problem. All my outputs work well as you told me to set it up.

My understanding of the RTD temp probes is that you do not need a struck command but have to linearize it. Is this correct. So how do I send it over from the EX- RC1 and see it on the vision 130.

Share this post

Link to post

Share on other sites

The first RTD module sensors are mapped to MI 11 .. 14 in the hardware configuration.

In the original program I modified and posted for you, I was sending all 16 registers. You have modified this to 4 in the program you posted back. Reason for this unknown.

I did not have the hardware to test these programs so what I posted back in the other thread may not have worked. The fact that you're still asking tells me there is still an error in the logic.

Here is the rung that actually sends the data from EX-RC#2 to the V130:

So let's do some basic ladder troubleshooting - when you go online, does the value of MI 2040 ever go to 1? If not, the data will never be sent. The comment above the line states that the logic should be MI2040 = 0, but this is not what the block is doing.

Look at the Help on the UniCAN send block, specifically the status information:

So if the MI 2040 status = 1 you shouldn't be sending the message anyway. The network is busy.